JP6720942B2 - Duplex stainless steel with excellent corrosion resistance and hydrogen embrittlement resistance - Google Patents

Description

The present invention relates to a duplex stainless steel having excellent corrosion resistance and hydrogen embrittlement resistance. The duplex stainless steel of the present invention is, in particular, a stainless steel material and a steel pipe using the stainless steel material, which is used in an environment in which hydrogen enters the steel material due to a corrosive environment such as acid, chloride, carbon dioxide and hydrogen sulfide, Alternatively, it can be suitably used for a pressure accumulator used in a high-pressure hydrogen environment.

In the case of stainless steel, Cr contained in the steel material is preferentially oxidized in the atmosphere and in a solution, and an oxide layer mainly composed of very thin Cr ₂ O ₃ is formed on the surface of the steel material, so that the steel material has high corrosion resistance. Is. Due to this high corrosion resistance, stainless steel has been used particularly as a piping material in an environment where carbon dioxide gas and hydrogen sulfide are present. In recent years, with the depletion of oil and natural gas, excavation has been carried out at sites where the corrosive environment is more severe, and materials having higher corrosion resistance than conventional stainless steel are being demanded.

The stainless steel used in such an environment is required to have not only the above corrosion resistance but also hydrogen embrittlement resistance. That is, the corrosion caused in the stainless steel due to the severe corrosive environment is slight, the cross-sectional area of the steel pipe reduced by the corrosion is negligible, and the strength of the steel pipe is guaranteed, or the fluid transfer inside the steel pipe is completely affected. Even if it does not exist, there is a concern that hydrogen generated by the above-mentioned slight corrosion diffuses into the stainless steel, reduces the cohesive energy of the steel structure of the stainless steel, and causes cracks (hydrogen embrittlement) penetrating the steel material. Therefore, in order to ensure the long-term durability of stainless steel, it is necessary to guarantee hydrogen embrittlement resistance in a severe corrosive environment.

The diffusion coefficient of hydrogen in steel varies depending on the structure of the steel. For example, the diffusion coefficient in ferrite having a body-centered cubic structure is about two orders of magnitude higher than the diffusion coefficient in austenite having a face-centered cubic structure. Therefore, austenitic stainless steel is superior in hydrogen embrittlement resistance to ferritic or martensitic stainless steel.

However, in order to stabilize stainless steel as austenite in various temperature regions, it is necessary to add a large amount of Ni, and further increase the amounts of Cr and Mo, which are ferrite formers, in order to improve the corrosion resistance of stainless steel. In that case, the austenite structure cannot be maintained unless the amount of Ni is increased accordingly, resulting in extremely high material cost. Therefore, a technique for imparting high hydrogen embrittlement resistance to stainless steel with reduced Ni content is industrially important.

For example, in Patent Document 1, Cu: 0.2 to 2%, Ni: 5 to 6.5%, Cr: 23.0 to 27.0%, Mo: 2.5 to 3.5% as corrosion resistant elements, In a duplex stainless steel containing W: 1.5 to 4% and N: 0.24 to 0.4% as essential elements, a σ phase sensitivity index, a strength index and a resistance index, which are respectively represented by the concentrations of chemical components. A technique for defining the pitting corrosion index in a predetermined range is disclosed.

Moreover, in patent document 2, Ni:1.0-10.0%, Cr:20.0-25.0%, Mo:2.0-5.0%, and N:00.10 are used as a corrosion-resistant element. In duplex stainless steel containing 0.20% as an essential element, 0.01 to 0.50% of Ta is added to positively form a sulfide or oxide containing Ta, thereby lowering the corrosion resistance. Techniques for suppressing the formation of MnS and Cr oxides that cause the above are disclosed.

JP, 2014-043616, A JP, 2016-089263, A

However, although the techniques described in Patent Documents 1 and 2 may contribute to the improvement of the corrosion resistance of the duplex stainless steel, when atomic hydrogen adsorbed on the surface of the stainless steel diffuses inside the stainless steel, It has no function of preventing the embrittlement of steel. In fact, the examples of Citations 1 and 2 do not describe any evaluation regarding hydrogen embrittlement.

Hydrogen embrittlement of duplex stainless steel can sufficiently occur even if the local hydrogen concentration diffused in the steel is about several ppm or less, so for some reason the corrosive environment temporarily becomes severe and slight local corrosion occurs. However, the occurrence of hydrogen embrittlement cannot be denied when exposed to a high-pressure hydrogen environment. Therefore, it is difficult to secure long-term reliability with the techniques disclosed in Patent Documents 1 and 2.

The present invention has been made in view of such circumstances, and is a duplex stainless steel having excellent corrosion resistance and hydrogen embrittlement resistance even in an environment where corrosion factors such as chloride, carbon dioxide and hydrogen sulfide are present. Is provided at low cost.

The present inventors have conducted the earnest research to solve the above problems, and as a result, obtained the following findings. That is, in a duplex stainless steel having a structure consisting of at least a ferrite phase and an austenite phase, and having a reduced Ni content so that it can be manufactured at low cost, the range of the volume fraction of the austenite phase is defined and the hydrogen embrittlement resistance By optimizing the chemical composition from the viewpoint, hydrogen that enters through the ferrite, which has a larger hydrogen diffusion coefficient than austenite, is trapped in the steel, and as a result, the hydrogen embrittlement resistance of duplex stainless steel is dramatically improved. Can be made

The present invention is based on the above findings, and its gist configuration is as follows.

1. In mass %,
C: 0.05% or less,
Si: 0.03 to 1.0%,
Mn: 0.05-2.0%,
P: 0.05% or less,
S: 0.005% or less,
Cr: 17.0 to 28.0%,
Ni: 4.0 to 18.0%,
Mo: 0.1-6.0%,
B: 0.031 to 2.0%, and N: 0.006 to 0.4% or less,
The balance has a composition of Fe and inevitable impurities,
Duplex stainless steel excellent in corrosion resistance and hydrogen embrittlement resistance, having a structure of at least a ferrite phase and an austenite phase and having a volume fraction of the austenite phase of 45 to 95%.

2. The above component composition is further mass%,
Al: 0.005-0.5%,
Sn: 0.005 to 0.30%,
Sb: 0.005-0.30%
Cu: 0.01 to 3.0%,
Co: 0.01-2.0%,
Nb: 0.001-0.3%,
Ti: 0.001 to 0.30%,
V: 0.001-0.3%,
Zr: 0.0005 to 0.30%,
Ta: 0.0005 to 0.30%,
Mg: 0.0005 to 0.01%, and Ca: 0.0005 to 0.01%, 1 or 2 or more selected from the group consisting of, containing 1 or more excellent corrosion resistance and hydrogen embrittlement resistance Duplex stainless steel.

The duplex stainless steel material according to the present invention can maintain excellent hydrogen embrittlement resistance and corrosion resistance for a long period of time in a corrosive environment containing a large amount of chloride, hydrogen sulfide and carbon dioxide gas as compared with the conventional ones, and therefore various types of oil wells and natural gas It can be used for various equipment including piping, and can cope with stricter excavation environment due to resource depletion. In addition, it can be applied to equipment related to hydrogen stations such as hydrogen pressure accumulators.

It is a schematic diagram which shows the structure of a low strain rate tensile stress corrosion cracking test piece.

Next, a method for carrying out the present invention will be specifically described. The following description shows preferred embodiments of the present invention, and the present invention is not limited to the following description.

[Ingredient composition]
First, the reason why the composition of the duplex stainless steel material of the present invention is limited to the above range will be described. In addition, the "%" display regarding a component shall mean the mass% unless there is particular notice.

C: 0.05% or less C is an element that enhances the strength of steel and contributes to stabilization of the austenite phase. In the present invention, 0.05% is added as the upper limit in order to secure the desired strength. However, the addition of more than 0.05% is not preferable because it promotes the formation of chromium carbide and reduces the corrosion resistance of stainless steel. Therefore, the amount of C is set to 0.05% or less. The range is preferably 0.03% or less.

Si: 0.03 to 1.0%
Si is an element added as a deoxidizing agent and contributes to stabilization of the ferrite phase. Addition of more than 1.0% not only lowers the toughness and workability of steel, but also accelerates the formation of the σ phase and lowers the corrosion resistance. On the other hand, addition of less than 0.03% cannot sufficiently contribute as a deoxidizing agent for steel. Therefore, the amount of Si is set to the range of 0.03 to 1.0%. Preferably it is 0.05 to 0.60% of range.

Mn: 0.05-2.0%
Mn is an element that enhances the strength of steel, and in the present invention, it is added in an amount of 0.05% or more to obtain a desired strength. However, the addition of more than 2.0% is not preferable because it accelerates the formation of MnS and reduces the corrosion resistance. Therefore, the Mn content is set to the range of 0.05 to 2.0%. It is preferably in the range of 0.07 to 1.60%.

P: 0.05% or less P is a harmful element that segregates at grain boundaries and reduces the toughness of steel, so it is desirable to reduce it as much as possible. In particular, if the content of Ni exceeds 0.05%, the toughness is significantly reduced. Therefore, the P amount is set to 0.05% or less. It is preferably 0.03% or less.

S: 0.005% or less S is a harmful element that forms MnS, which is a non-metallic inclusion, as a starting point of local corrosion, and reduces local corrosion resistance. Therefore, it is desirable to reduce S as much as possible. In particular, if the content exceeds 0.005%, the local corrosion resistance is significantly lowered. Therefore, the upper limit of the allowable amount of S is 0.005%. It is preferably 0.003% or less.

Cr: 17.0 to 28.0%
Cr is a main element that forms a passivation film of duplex stainless steel, and is an essential element for ensuring corrosion resistance. The corrosion resistance of stainless steel improves as the Cr content in the steel increases, but since it has the effect of stabilizing the ferrite phase, in order to keep the ferrite fraction in the duplex stainless steel within a certain range (austenite content In order to secure the ratio), Ni, which has the effect of stabilizing austenite, must be increased according to the amount of Cr added. If Cr is less than 17.0%, sufficient corrosion resistance cannot be exhibited, which is not preferable. On the other hand, addition of Cr in excess of 28.0% not only deteriorates hot workability, but also increases the amount of Ni for maintaining the ferrite fraction within a certain range, resulting in high cost, which is not preferable. .. Therefore, the Cr amount is set to 17.0 to 28.0%. Preferably, it is 18.0 to 25.0%.

Ni: 4.0-18.0%
Ni is an element effective in improving the corrosion resistance of duplex stainless steel, and also contributes to stabilization of the austenite phase. Since the hydrogen diffusion coefficient in steel becomes smaller in austenite having a face-centered cubic structure, in order to secure hydrogen embrittlement resistance, the austenite fraction must be maintained at a certain level or higher and 4.0% or higher. The addition of Ni is essential. On the other hand, the addition of Ni in excess of 18.0% is not preferable because it promotes the formation of the σ phase in the steel and reduces the workability. Therefore, the Ni content is set to 4.0 to 18.0%, preferably 5.0 to 16.0%.

Mo: 0.1-6.0%
Mo is an extremely effective element for improving the corrosion resistance of duplex stainless steel. However, addition of less than 0.1% does not sufficiently improve the corrosion resistance. On the other hand, addition of Mo in excess of 6.0% not only lowers the hot workability, but also contributes to the stabilization of the ferrite phase by Mo and causes a decrease in the austenite fraction, thus reducing hydrogen embrittlement resistance. To do. Therefore, the amount of Mo is set to 0.1 to 6.0%, preferably 0.5 to 5.0%.

B: 0.031 to 2.0%
B is an element that contributes to the stabilization of the austenite structure in the duplex stainless steel, and is an essential addition element that is extremely effective in improving the hydrogen embrittlement resistance while suppressing the amount of Ni added. Further, since B is an element that forms sulfides preferentially over Mn, the addition thereof can suppress the formation of MnS, which is the starting point of local corrosion, and improve the corrosion resistance. Furthermore, since the formation of the above-mentioned sulfide suppresses the precipitation of sulfur-based inclusions at the grain boundaries, the workability is improved. In order to exhibit these effects, 0.031% or more must be added. On the other hand, if added in excess of 2.0%, coarse oxides are deposited, rather reducing the workability. Therefore, the B content is set to 0.031 to 2.0%, preferably 0.05 to 1.6%.

N: 0.006-0.40%
N is an element that significantly improves the corrosion resistance of the duplex stainless steel and stabilizes the austenite phase. When the amount of N added is less than 0.006%, the effect of improving the corrosion resistance is little expressed. On the other hand, when N is added in excess of 0.40%, toughness and workability deteriorate. Therefore, the N amount is set to 0.006 to 0.40%, preferably 0.01% to 0.35%.

The duplex stainless steel in one embodiment of the present invention may have a composition of the above elements and the balance being Fe and inevitable impurities.

In addition, the duplex stainless steel according to another embodiment of the present invention may optionally contain one or more elements of the above-described component composition described below.

Al: 0.005-0.5%
Al is an element that acts as a deoxidizer. When Al is added, the Al content is 0.005% or more. On the other hand, when Al is added in excess of 0.5%, not only the toughness of the steel is lowered, but also the aluminum oxide formed in the steel becomes a starting point of local corrosion and the corrosion resistance is lowered. Therefore, the upper limit of the amount of Al is 0.5%.

Sn: 0.005-0.30%
Sn is an element that improves the corrosion resistance, and it is necessary to add 0.005% or more in order to exhibit the effect. On the other hand, if added in excess of 0.30%, hot workability and toughness deteriorate. Therefore, when Sn is added, the Sn amount is set to 0.005 to 0.30%, preferably 0.01 to 0.20%.

Sb: 0.005-0.30%
Sb is an element that not only improves the corrosion resistance of duplex stainless steel, but also forms carbides and sulfides, acts as trap sites for hydrogen that diffuses the ferrite phase, and improves hydrogen embrittlement resistance of duplex stainless steel. is there. If the amount of Sb added is less than 0.005%, the effect is insufficiently expressed, while if it exceeds 0.30%, the hot workability is significantly reduced. Therefore, when Sb is added, the amount of Sb is set to 0.005 to 0.30%, preferably 0.01 to 0.205%.

Cu: 0.01-3.0%
Cu is an element that improves the corrosion resistance of duplex stainless steel and stabilizes the austenite phase. When the amount of addition of Cu is less than 0.01%, the effect of improving the corrosion resistance is small. On the other hand, if Cu is added in excess of 3.0%, the toughness and hot workability deteriorate. Therefore, when Cu is added, the Cu content is set to 0.01 to 3.0%, preferably 0.05% to 2.5%.

Co: 0.01-2.0%
Co is an additive element that improves the corrosion resistance of duplex stainless steel and stabilizes the austenite phase. When the amount of Co added is less than 0.01%, the effect of improving the corrosion resistance is little expressed. On the other hand, when Co is added to exceed 2.0%, the toughness and workability are deteriorated. Therefore, when Co is added, the amount of Co is 0.01 to 2.0%, preferably 0.05% to 2.0%.

Nb: 0.001-0.3%
Nb is an element that improves the corrosion resistance of the duplex stainless steel and enhances the strength of the steel material, and can be arbitrarily added depending on the required strength. In order to obtain the above effect, the Nb content needs to be 0.001% or more. On the other hand, if Nb is added in excess of 0.3%, the toughness decreases. Therefore, when Nb is added, the amount of Nb is set to 0.001 to 0.3%, preferably 0.005 to 0.2%.

Ti: 0.001 to 0.30%
Like Nb, Ti is an element that improves the corrosion resistance of the duplex stainless steel and enhances the strength of the steel material, and can be arbitrarily added depending on the required strength. In order to obtain the above effect, the Ti content needs to be 0.001% or more. On the other hand, if Ti is added in excess of 0.30%, the toughness decreases. Therefore, when adding Ti, the amount of Ti is made 0.001 to 0.30%, preferably 0.005 to 0.20%.

V: 0.001-0.3%
Similar to Nb and Ti, V is an element that improves the corrosion resistance of the duplex stainless steel and enhances the strength of the steel material, and can be added arbitrarily depending on the required strength. In order to obtain the above effect, the V content needs to be 0.001% or more. On the other hand, if V is added in excess of 0.3%, the toughness decreases. Therefore, when V is added, the amount of V is set to 0.001 to 0.3%, preferably 0.005 to 0.2%.

Zr: 0.0005 to 0.30%
Zr is an element that contributes to improving the corrosion resistance of duplex stainless steel. That is, the precipitation of MnS, which is the starting point of local corrosion, by substitution and precipitation suppresses the dissolution of MnS. In order to realize this function, 0.0005% or more must be added. On the other hand, if it is added in an amount exceeding 0.30%, nitrides will be precipitated, and the toughness and workability of the duplex stainless steel will be reduced. Therefore, when Zr is added, the amount of Zr is 0.0005 to 0.30%, preferably 0.001 to 0.20%.

Ta: 0.0005 to 0.30%
Ta, like Zr, is an element that contributes to the improvement of the corrosion resistance of duplex stainless steel. That is, the precipitation of MnS, which is the starting point of local corrosion, by substitution and precipitation suppresses the dissolution of MnS. In order to realize this function, 0.0005% or more must be added. On the other hand, if it is added in an amount exceeding 0.30%, nitrides will be precipitated, and the toughness and workability of the duplex stainless steel will be reduced. Therefore, when Ta is added, the Ta amount is set to 0.0005 to 0.30%, preferably 0.001 to 0.20%.

Mg: 0.0005-0.01%
Like B, Mg is an element that forms sulfide preferentially over Mn. Therefore, the addition of Mg can suppress the formation of MnS, which is the starting point of local corrosion, and improve the corrosion resistance. Furthermore, since the formation of the above-mentioned sulfide suppresses the precipitation of sulfur-based inclusions at the grain boundaries, the workability is improved. In order to exert these effects, 0.0005% or more must be added. On the other hand, if it is added in excess of 0.01%, a coarse oxide is deposited, which rather reduces the workability. Therefore, when adding Mg, the amount of Mg is set to 0.0005 to 0.01%, preferably 0.0008 to 0.005%.

Ca: 0.0005-0.01%
Like B and Mg, Ca is an element that forms sulfide preferentially over Mn. Therefore, the addition of Ca can suppress the formation of MnS, which is the starting point of local corrosion, and improve the corrosion resistance. Furthermore, since the formation of the above-mentioned sulfide suppresses the precipitation of sulfur-based inclusions at the grain boundaries, the workability is improved. In order to exert these effects, 0.0005% or more must be added. On the other hand, if it is added in excess of 0.01%, a coarse oxide is deposited, which rather reduces the workability. Therefore, when Ca is added, the amount of Ca is set to 0.0005 to 0.01%, preferably 0.0008 to 0.005%.

[Ingredient composition]
Next, the reason why the structure of the duplex stainless steel material of the present invention is limited to the above range will be described.

The duplex stainless steel of the present invention has a structure including at least a ferrite phase and an austenite phase. In addition, when only the peaks of α-Fe and γ-Fe are observed when the X-ray diffraction measurement is performed by the method described in the examples, it is considered that the structure has a ferrite phase and an austenite phase.

Austenite fraction: 45-95%
The volume fraction of the austenite phase in the above structure should be 45 to 95%. As described above, the hydrogen diffusion coefficient of the ferrite phase is two orders of magnitude higher than that of the austenite phase, so when the volume fraction of the austenite phase is less than 45%, the ferrite fraction becomes relatively high and the hydrogen resistance is high. Brittleness is greatly reduced. On the other hand, when the volume fraction of the austenite phase exceeds 95%, Cr and Mo that are ferrite formers are concentrated in the remaining slight ferrite phase, and the concentrations of Cr and Mo in the austenite phase having a high fraction are reduced. When such a steel structure is exposed to a severe corrosive environment, the austenite phase, which is inferior in corrosion resistance to the ferrite phase, is preferentially dissolved, so that the corrosion resistance of the steel as a whole decreases. Therefore, the volume fraction of the austenite phase is 45 to 95%, preferably 50 to 90%.

[Production method]
The duplex stainless steel of the present invention can be manufactured by any method without particular limitation. For example, a steel slab having the above-described composition is hot-rolled at a finish rolling end temperature of 900 to 1000°C to form a steel plate, and then cooled to a cooling stop temperature of 400 to 480°C at a water cooling rate of 10 to 16°C/s. Can be obtained by

Hereinafter, the present invention will be described in detail based on examples.

(Production of steel)
Steels having various component compositions shown in Table 1 are melted in a vacuum melting furnace to form steel ingots, or in a converter to form steel slabs by continuous casting, which are produced at 1150° C. for 1 hour. After reheating, hot rolling was performed at a finish rolling finish temperature of 900 to 1000° C. to obtain a thick steel plate having a plate thickness of 25 mm, and then cooled to a cooling stop temperature of 400 to 480° C. at a water cooling rate of 10 to 16° C./s.

The volume fraction of the austenite phase of each of the obtained stainless steel sheets was measured by the following method. Further, as described below, a low strain rate tensile stress corrosion cracking test and a corrosion resistance test were carried out to evaluate hydrogen embrittlement resistance and corrosion resistance.

(Volume of austenite phase)
From the center portion of the thickness of the obtained stainless steel plate, one 20×20×6 mmt test piece was taken for each steel type. After polishing the measurement surface with emery paper No. 600, XRD (X-ray diffraction) was measured, and the volume fraction of the austenite phase was determined from the obtained peak areas of α-Fe and γ-Fe.

(Low strain rate tensile stress corrosion cracking test)
Two low strain rate tensile stress corrosion cracking test pieces shown in FIG. 1 were taken from each of the steel types from the center of the thickness of the obtained stainless steel plate in parallel with the rolling direction. One is in the air and the other is in an electrolyte with a constant current density applied to the test piece using a galvanostat, and a constant amount of hydrogen is constantly generated on the surface of the steel material. The test was conducted. The strain rate was 3.3×10 ⁻⁶ /s. The electrolyte used was 3% NaCl+0.3% NH ₄ SCN, and the current density was 30 mA/cm ² .

After the test was completed, the aperture value in each test was obtained, and the aperture value obtained by applying hydrogen was divided by the aperture value in the atmosphere to obtain a value (aperture ratio). A drawing ratio of 90% or more was marked with ⊚, 80% or more was marked with ◯, 60% or more was marked with Δ, and less than 60% was marked with x. The closer the drawing is to 100%, the better the hydrogen embrittlement resistance.

(Corrosion resistance test)
The corrosion resistance was evaluated by an immersion test in which the test piece was immersed in the solution. First, five test pieces of 40×40×6 mmt were taken for each steel type from the center portion of the thickness of the obtained stainless steel plate. After polishing all 6 surfaces with No. 600 emery paper, 5 surfaces were sealed with tape leaving the surface, and cut off so as not to come into contact with the solution during the immersion test. As the solution, a solution was prepared by mixing 4.0 mol/l CH ₃ COOH aqueous solution and CH ₃ COONa to adjust the pH to 2.3 and then adding NaCl to a concentration of 5.0 wt %.

In the immersion test, after the solution was degassed with N ₂ gas in advance, the test piece was put so that the test surface faced upward, and a gas consisting of 20% H ₂ S and the balance of CO ₂ was added at 50 ml/min in the solution. And allowed to stand for 7 days at room temperature. After the test, N ₂ gas was blown into the solution to remove H ₂ S, the test piece was taken out, washed with water and dried, and the presence or absence of corrosion was visually observed. The case where corrosion was not observed in all 5 pieces was rated as ○, the case where only one piece was corroded was marked as △, and the case where corrosion was recognized in two or more pieces was marked as x.

The results of each test are shown in Table 1. Steel No. 3 having a chemical composition within the range specified in the present invention and having a volume ratio of the austenite phase of 45 to 95%. 1 to 40 showed good test results (evaluation Δ or higher). On the other hand, steels that fall outside the range of the chemical composition specified in the present invention, and steels that meet the range of the specified chemical composition but have an austenite phase ratio of less than 45% (steel Nos. 41 to 46) have a result. Poor (evaluation x).

Claims (2)

In mass %,
C: 0.05% or less,
Si: 0.03 to 1.0%,
Mn: 0.05-2.0%,
P: 0.05% or less,
S: 0.005% or less,
Cr: 17.0 to 28.0%,
Ni: 4.0 to 18.0%,
Mo: 0.1-6.0%,
B: 0.031 to 2.0%, and N: 0.006 to 0.4% or less,
The balance has a composition of Fe and inevitable impurities,
It consists ferrites phase and austenite phase, the volume fraction of the austenite phase has a tissue 45 to 95% the corrosion resistance and hydrogen embrittlement resistance excellent duplex stainless steel. The above component composition is further mass%,
Al: 0.005-0.5%,
Sn: 0.005 to 0.30%,
Sb: 0.005-0.30%
Cu: 0.01 to 3.0%,
Co: 0.01-2.0%,
Nb: 0.001-0.3%,
Ti: 0.001 to 0.30%,
V: 0.001-0.3%,
Zr: 0.0005 to 0.30%,
Ta: 0.0005 to 0.30%,
The corrosion resistance and hydrogen embrittlement resistance according to claim 1, containing 1 or 2 or more selected from the group consisting of Mg: 0.0005 to 0.01% and Ca: 0.0005 to 0.01%. Excellent duplex stainless steel.

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